1. Field of the Invention.
The present invention relates to polyamide/polyester composite fibers with polymer grafting. Another aspect of this invention relates to a method of producing such fibers.
2. Prior Art.
Fibers have previously been prepared from blends of polyamides with minor amounts of polyesters such as poly(ethylene terephthalate). Intimate mixing before and during the spinning process has been recognized as necessary to achieve good properties in such blended fibers. It is furthermore known that the fine dispersions in fibers of polymer blends are achieved when both phases have similar characteristics such as melt viscosity. See D.R. Paul, "Fibers From Polymer Blends" in Polymer Blends, vol. 2, pp. 167-217 at 184 (D.R. Paul & S. Newman, ehs., Academic Press 1978).
Organophosphites such as triphenylphosphites are known to cause reaction of certain polymer blends such as nylon 6/nylon 66, nylon 6/poly(ethylene terephthalates) and nylon 6/poly(butylene terephthalate) to form graft or block copolymers which can be spun into fibers. For example, U.S. Pat. No. 4,417,031, and S. Aharoni, Polymer Bulletin, vol. 10, pp. 210-214 (1983) disclose a process for preparing block and/or graft co-polymers by forming an intimate mixture of two or more polymers at least one of which includes one or more amino functions, as for example a nylon, and at least one of the remaining polymers includes one or more carboxylic acid functions, as for example a polyester, and a phosphite compound; and thereafter heating the intimate mixture to form the desired block and/or graft copolymers. U.S. Pat. No. 4,417,031 discloses that such copolymers can be spun into fibers.